Question: What is the significant landmark in the capital of the Achaemenid Empire?
Paraphrase: What is the critical point of interest within the capital of the Achaemenid Realm?
SPARQL (Wikidata):  select distinct ?obj where { wd:Q389688 wdt:P36 ?obj . ?obj wdt:P31 wd:Q2319498 } 
Answer: Persepolis, Susa